Unitary hinge



Dec. 6, 1966 H. WOLF 3,289,877

UNITARY HINGE Filed March 21, 1966 4 Sheets-Sheet 1 I N VEN'I UR.

HA WOLF PATENT AGENT Dec. 6, 1966 H. WOLF 3,289,877

UNITARY HINGE Filed March 21, 1966 4 Sheets-Sheet 2 17 FIG. 5

LF Z PATENT AGENT HANS W I N VEN UR.

Dec. 6, 1966 I H. WOLF 3,289,877

UNITARY HINGE Filed March 21, 1966 4 Sheets-Sheet 5 1 N VEN TOR.

PATENT AGENT H. WOLF UNITARY HINGE Dec. 6, 1966 4 Sheets-Sheecv 4 Filed March 21, 1966 FIG.14

INVEN/UR. NS W OLF J% PATENT AGENT United States Patent 3,289,877 UNITARY HINGE I-Ians Wolf, Deggendorf (Danube), Germany, assignor to Westhem Corporation Limited, Toronto, Ontario, Canada, a corporation of Canada Filed Mar. 21, 1966, Ser. No. 536,117 Claims priority, application Germany, Mar. 20, 1963,

W 34,224; Nov. 22, 1965, W 36,137

22 Ciairns. (Cl. 22031) This is a continuation-in-part of my pending application Serial No. 352,042, filed March 16, 1964.

This invention relates to hinge or clip structures. More particularly, this invention relates to a unitary hinge or clip structure having a spring-biasing action and to articles incorporating such a hinge.

The single piece hinge of the present invention may be used for many different purposes, such as for doors, windows, box lids, etc., and also may serve as a clip or clamp structure for tightly holding together sheets of paper or the like. It will be appreciated that a hinge structure embodying this invention can be used for many purposes and is particularly suitable where it is desired to have two members connected by the hinge held by spring action in end-to-end positionor in overlying relation or in some other angular orientation.

The main object of the present invention is to provide a novel hinge structure consisting of only a single component.

A further object of the invention is to provide a hinge which, in some circumstances, may be formed in one piece with the door, window, box lid or other structure or article with which it is used.

Another object of the invention is to provide a hinge structure which requires no maintenance, such as oiling, or the like, and which will not break down or squeak due to lack of maintenance.

Still another object of the invention is to provide a hinge structure which is non-corrosive, even when subjected to severe environments, such as salt spray, chemical fumes, or the like.

A further object of the invention is to provide a unitary hinge structure that is capable of exerting a clamping action, but which does not use a separate spring member.

Still a further object of the invention is to provide a unitary hinge structure having novel biasing means for securely holding the fastening plate portions of the hinge in overlying relation with respect to each other or in endto-end relation or positioned at other predetermined angles relative to one another.

Other advantages of the invention lie in the adaptability of the hinge to mass production and its relatively low manufacturing cost, as well as its durability under continuous use.

This invention will become more apparent from the following detailed description, taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a side elevation, in the open position, of a prior art hinge structure composed of nine separate parts;

FIG. 2 is a side elevation of the hinge of FIG. 1 with the fastening plates disposed at an angle of 90 relative to each other;

FIG. 3 is a side elevation similar to FIG. 2 showing the fastening plates disposed at an angle of approximately 45 relative to each other.

FIG. 4 is a side elevation similar to FIG. 3 showing the fastening plates in closed position, wherein they are clamped in overlying relation to each other;

FIG. 5 is a cross sectional view of a unitary hinge embodying this invention and which operates in a similar manner to the hinge of FIGS 1-4, FIGURE 5 being taken substantially along line 55 of FIG. 6;

FIG. 6 is a top plan view of the hinge shown in FIG. 5;

FIG. 7 is a side elevational view of the hinge of FIG. 5 in closed position and shows the fastening plates thereof folded back upon themselves;

FIG. 8 is a cross sectional View similar to FIG. 5, of a modified form of the invention;

FIG. 9 is a cross sectional view of the modified form of the hinge shown in FIG. 8 showing the fastening plates thereof in a transitional position;

FIG. 10 is a cross sectional view of the modified form of the hinge'shown in FIG. 8 showing the hinge in closed position with the fastening plates thereof folded back upon themselves;

FIG. 11 is a cross sectional view of a hinge like that shown in FIG. 5 but modified to tend always to return to the open or extended position thereof;

FIG. 12 is a cross sectional view of the hinge shown in FIG. 11 in its closed or overlapping position;

FIG. 13 is a cross sectional view of a ring box in open position, the ring box having a hinge embodying this invention moulded integrally therewith;

FIG. 14 is a cross sectional view taken on line 1414 of FIG. 15; and

FIG. 15 is a plan view of the ring box showing it in closed position.

All drawings are diagrammatic. The exact dimensions and relationship of the parts must be calculated carefully for each size and different application of the hinge. To

'a certain extent the approach is empirical.

Referring to the drawings in greater detail, and particularly the hinge of the prior art shown in FIGS. l4, the main portion of the hinge consists of two fastening plates 1 and 2. pivotally connected to each other by a hinge pin 3. Link members 4 and 5 are pivotally connected together at one end by a pivot pin 8 or the like and are pivotally connected at their opposite ends to fastening plates 1 and 2 respectively by means of pivot pins 6 and 7 respectively, or the like. Link member 4 is shorter in length than link member 5 with the respective pivot pins 6 and 7 being different distances away from hinge pin 3, and the axis of pivot pin 8 is disposed in laterally offset position from the axis of hinge pin 3 by the distance indicated by reference numeral a, so that the axis of hinge pin 3 is disposed laterally further from the axis of pivot pin 6 than is the axis of pivot pin 8 by the distance represented by a.

A leaf spring 10 is connected to the back of fastening plate 1 by bolts or rivets 11 and 12. The free end of spring 19 diverges outwardly from plate 1, and is engaged by a hook portion 13 of link member 4. This mechanism provides a spring action for the hinge to normally retain the fastening plates 1 and 2 in the open or extended position, as indicated in FIG. 1, or in the closed position, as shown in FIG. 4. In the open position of the hinge, the end of leaf spring 10 that overlies link member 4 is disposed in angular relation with fastening plate 1 and through link members 4 and 5 retains plates l and 2 in aligned end-to-end relation. Pivot pin 8 is offset vertically relative to hinge pin 3 by a distance represented by b in FIG. 1.

Referring to FIG. 2, as fastening plate 2 is turned in the direction of arrow 14 relative to fastening plate 1 and about hinge pin 3, link member 5 pivots about pivot pin 7 and pulls on pivot pin 8 causing link member 4 to pivot clockwise about pivot pin 6 relative to plate 1 against the spring-biasing action of leaf spring 10, which tends to return link members 4 and 5 and plate 2 to the positions thereof shown in FIG. 1. If the pivoting of plate 2 continues until plates 1 and 2 are disposed at approximately degrees to each other, as indicated in FIG. 2, since the direction of action of the returning spring force is represented by the longitudinal axis c of link member 5, and since the spring force vector passes through the axis of binge pin 3 and pivot pins 7 and 8, the force exerted by spring 11 through link members 4 and 5 on fastening plate 2 theoretically is unable to return plate 2 to the position of FIG. 1. Thus, in spite of the strong biasing force provided by spring 10 flexed to its maximum extent, as shown in FIG. 2, all of the parts theoretically remain in the position shown in FIG. 2, and the fastening plates 1 and 2 remain disposed at approximately 90 degrees with respect to each other. When the hinge is in the position of FIG. 2 it is at its turning point and is in a condition of unstable equilibrium. In this position, distances a and b are at a minimum.

If fastening plate 2 is pivoted further about hinge pin 3, as indicated in FIG. 3, leaf spring 10 begins returning to its original position by flexing upwardly in a counterclockwise direction and draws link members 4 and 5 with it. Although the return force of spring 10 in this position now is less than it was when the spring was in the position shown in FIG. 2, the force vector along longi tudinal axis is displaced from the axis of hinge pin 3. Thus, spring 10, acting through link members 4 and pulls fastening plate 2 in the direction of arrow 14 into side-by-side overlying relation with fastening plate 1, as shown in FIG. 4, so that the plates are disposed parallel to each other and are clamped together by the action of spring 10, since spring continues to urge link member 5 in a clockwise direction. In the position of the components shown in FIG. 4, distances (1 and b are less than in FIG. 1, but greater than in FIGS. 2 or 3.

The action of spring 10 thus retains the fastening plates in the extended position of FIG. 1 or in side-by-side relation as indicated in FIG. 4. At various points between these positions, the plates will be returned automatically to the positions shown in either FIGS. 1 or 4.

A hinge embodying this invention, as shown in FIGS. 5, 6 and 7, has the nine separate parts of the hinge of FIGS. 1-4 incorporated into a single component, thus rendering such hinges adaptable to mass production at very low cost. The hinge of the invention is preferably made of polypropylene, which has a highly crystalline structure, giving the hinge high tensile strength and the quality of remaining tough, flexible and resilient even at low temperatures. Other flexible synthetic thermoplastic materials having the characteristic of withstanding continued flexing without breaking, such as nylon, also may be used for moulding the hinge structure, but polypropylene thus far has been found to be the most suitable and the durable material for the hinge, particularly with respect to its ability to withstand continued flexing without breakage, and its ability to return to its original position after repeated bending operations.

Referring to the form of the invention shown in FIGS. 57, the fastening plates 1' and 2, which may be provided with screw holes 25, are joined by a thin layer of material formed integral with plates 1 and 2 and which forms flexible bending lines 20 and 21 to allow the thicker and relatively rigid fastening plates 1' and 2 to pivot relative to each other. As shown, these bending lines 20 and 21 are formed adjacent V-shaped recesses in the material of fastening plates 1 and 2.

The centre portion of fastening plate 1' is provided with a resilient member which forms a spring arm 16 that t is separated from plate 1 along its side edges and that is integrally connected at 26 to plate 1'. Spring arm 16 is disposed in angular relation to fastening plate 1 in the same manner as link member 4 and spring 10 of the hinge shown in FIG. 1.

The opposite longitudinaledge of member 16 is joined at 17 to a comparatively thin link member or connecting arm 19 which is separated along its side edges from fastening plate 2 and which is joined thereto at 18 along one of its longitudinal edges. The joints 17 and 18 form thin, flexible bending lines, so that connecting arm 19 is free to pivot about these bending lines. Connecting arm 19 may be thin and flexible. Since no compressive force is applied to it, it need not be stiff or resilient, although in practice it will have both the latter characteristics.

Member 16 must be resilient, and by this is meant that it must be capable, when deflected, of providing a spring biasing action or restoring force that tends to return it to its original position. The whole of member 16 need not be resilient, however. Thus, it would be suflicient if its connection 26 to fastening plate 1 or some other part of member 16 were resilient and the remainder of member 16 quite rigid. In practice member 16 as a whole will be resilient but relatively stiff, but where herein the term resilient member or terminology of like import is employed, it is to be construed broadly and is intended to include the various alternatives suggested in this paragraph.

Connecting arm 19 acts like link member 5, and bending lines 17 and 18 are the equivalent of pivot pins 8 and 7. Spring arm 16 performs the function of both link member 4 and spring 100. The connection 26 is substituted for pivot pin 6, and bending lines 20 and 21 are substituted for hinge pin 3 of the hinge shown in FIG. 1. Bending line 17 is laterally offset from the bending lines 20 and 21 by the distance a. By reason of the angular disposition of member 16, bending line 17 also is offset from bending lines 20 and 21 on one side of plates 1 and 2' and in a direction substantially perpendicular to the lateral offset by a distance represented by b.

As fastening plate 2' is pivoted clockwise relative to fastening plate 1 about bending lines 20 and 21, connecting arm 19 pivots inwardly along bending lines 17 and 18 drawing spring arm 16 in a clockwise direction and causing it to flex along connection 26 with respect to fastening plate 1.

The hinge operates in the same manner a the hinge of FIGS. 1-4 and comes to what could be called a turning point when plates 1' and 2 are disposed in a particular angular relationship to each other and maximum pull is exerted by spring arm 16. In this position, bending lines 17, 20, 21 and 1 8 are aligned, as are pivot pins 7 and 8 and hinge pin 3 in FIG. 2, so that theoretically spring arm 16 is unable to move plate 2' towards the open or closed position of the hinge.

As the turning point is passed and plate 2' is rotated further clockwise toward plate 1', the resilient biasing action or restoring force of spring arm 16 acting through connecting arm 19 pulls plate 2 into overlying clamping relation with plate 1', as shown in FIG. 7. When plates 1 and 2' are pivoted back from the overlying or closed position to the open or extended position, spring arm 16 resists the movement until the turning point has been passed, after which it pulls the plates back to the open position of the hinge by virtue of its restoring force.

When the plates 1 and 2' are in overlying position, spring arm 16 nearly has returned to its original position, but it is still sufliciently deflected to hold the plates snugly together or to clamp an article between them if desired. Distances a and b in FIG. 7 are slightly less than distances a and b in FIG. 5.

As aforementioned, a hinge embodying this invention preferably is moulded from polypropylene. This material with its crystalline structure experiences, because of a cold-stretching process taking'place at bending lines 17, 18, 20 and 21 during flexure, an orientation and consolidation of the molecules of the material. As a result of further flexing during use, increases in tensile and tearing strength result creating a hinge which is very strong at its bending lines. It has been found that with the hinge structure of the invention moulded out of polypropylene in this manner, the hinge will safely endure about onemillion bending cycles without failure of the highly stressed thin bending lines 17, 18, 20 and 21. It has been found that if the hinge is moulded with the major surfaces of the plates 1' and 2 in the angular relationship in which they will normally lie, the plates will tend to return to this original relationship.

A modified form of the invention is shown in FIGS. 8, 9 and 10. It will be noted that in this form of the invention, as shown in FIG. 8, the distances represented by a and b are somewhat less than in FIG. 5. The result is that there is more pull exercised by spring arm 16 when the plates 1 and 2 are in overlapped position. In the closed position of the hinge illustrated in FIG. 7, spring arm 16 has returned nearly to the position that it occupies in FIG. 5 and is exerting a comparatively slight pull on connecting arm 19, Whereas, in FIG. 10, spring arm 16 has not nearly returned to the original position of FIG. 8 and exerts considerable pull on arm 19. As will be hereinafter more fully described, by adjusting the lateral ofiset of bending lines 17 and 21 (or 17 and 21'), the clamping force between plate 1' and 2' when the hinge is closed can be regulated.

The major portion of the surface 16a of spring arm 16 in FIGS. 8, 9 and 10 in the opened and in the closed position of the hinge lies substantially in the same plane as the outer surface 1'a of plate 1' and does not protrude outwardly in angular relation with respect thereto, as in the hinges shown in FIGS. 1 and 5. This enables the hinge of FIGS. 8-10 to be mounted flush against a flat surface without modifying the surface, as might be necessary with the hinge shown in FIG. 5. Spring arm 16 is of substantially the same thickness as plate 1' at the point of connection 26' and flexes at this point when the hinge is moved from the position shown in FIG. 8 through the position shown in FIG. 9 to the position shown in FIG. 10. The spring arm is tapered or gradually reduced in thickness toward the end 27 thereof, as shown, which end, extends outwardly at an angular relation to the major outer surface 16's: of spring arm 16. This angularly disposed end 27 would extend into the space between members being joined by the hinge, and thus modification of the srrfaces of these members would not be necessary to provide a space into which end 27 could protrude.

End 27 is joined by flexible bending line 17 to connecting arm 19'. However, in this modified form of the inventian, connecting arm 19 is bent inwardly intermediate its ends. As the hinge is moved to the closed or overlapping position, as shown in FIGS. 9 and 10, connecting arm 19 flexes about bending line or bight portion 29, as Well as about bending lines 17' and 18', While spring arm 16 flexes resiliently at 26' and 27. In this embodiment, connecting arm 19 is preferably thin and resilient. However, it could be thick and rigid with only thin flexible bending lines 17', 18 and 29.

It will be noted in FIG. 8 that plates 1' and 2' are provided with inwardly directed recesses 30 on opposite sides of the bending lines between plates 1 and 2. This is to ensure that plates 1 and 2 may be disposed in flush overlying relation in the closed position, as shown in FIG. 10. It also will be noted from FIG. 10 that when this hinge is in its closed position, spring arm 16', which retains the hinge in this position, will not protrude in any way beyond wall Iia of the hinge, thus enabling the hinge to fit in a compact space.

FIGS. 11 and 12 show a modified hinge which tends to return to the open position at all angular positions of plates 1' and 2. The lateral oflset of bending lines 21' and 17' is indicated as +a, in contrast to the lateral offset indicated as -a in the hinges previously described. The offset b is substantially the same as in FIG. 8. As shown in FIG. 12, when the plate 1' is pivoted into overlapping relation with plate 2, bending lines 1 21' and 18 are not yet in alignment, i.e., the hinge has not yet passer its turning point. Thus, when the force holding plates 1' and 2' together is released, spring arm 16 will force the hinge to assume the fully opened position shown in FIG. 11.

By varying the lateral offset -|-a or a of bending lines 17' and 21, the turning point of the hinge may be varied 6 and the hold-closed force exerted by spring arm 16 or 16' increased or decreased. At the turning point, offset 12 is a minimum. Therefore the spring arm is at its maximum deflection and thus is exerting its maximum restoring force. Thus, when plates 1' and 2 come into overlapping position just after the turning point has been passed, near maximum closing pressure is applied thereto.

In general, if the dimension n in FIGS. 5 or 8 is increased (made longer), the turning point may be made to occur earlier, and if -a in FIGS. 5 or 8 is decreased (made shorter), the turning point may be made to occur later. An increase in a in the open position reduces the hold-closed force in the closed position, While, conversely, a decrease in a in the open position increases the hold-closed force in the closed position.

In some applications of the invention it may be desirable or necessary that one plate should move relative to the other in an arc of less than 180, and it is a feature of this invention that the hold-closed or hold-open position may be varied by providing stop means to limit the hinging movement of the parts.

It is a further feature of this invention that the hinge may be made integral with the article with which it is used. In fact it is contemplated that the most important applications of the invention will be in integrally moulded articles such as the ring box illustrated in FIGS. 13-15. Many of the parts in these figures correspond to parts in FIGS. 5-12 and in order to indicate this, the same reference numerals have been used, distinguished by two prime marks.

The ring box is injection moulded from polypropylene or the like thermoplastic material in one piece and in the open position of FIG. 13. After having been opened beyond the turning point, its lid returns automatically to the open position due to the memory of the spring hinge 40.

The box comprises a base 31 and a cover 32. The base 31 has a bottom 33, end walls 34, 34, a front sloping wall 35 and a rear sloping wall 36. The cover 32 has ends 37, 37 and curved front and rear walls 38 and 39.

The base and cover are hinged together by means of a hinge 40 made in accordance with this invention. The hinge may be made separately from and secured to the box, but preferably it is moulded integrally with the box as illustrated, whereby considerable saving in material and manufacturing cost is effected, and a neater, more compact and attractive article is obtained.

The rear walls of the base and cover are pivotally joined in end-to-end relation along their edges by thin flexible lines 28" and 21" formed adjacent V-shaped depressions in the outer surfaces of the rear walls 36 and 39. Spring arm 16" is formed integrally with the rear wall 39, which acts as a rigid plate similar to plate 1' of FIGS. 5 to 12 inclusive. Connecting arm 19" is connected along flexible bend line 17" to spring arm 16" and along flexible bend line 18" to rear wall 36, which forms a rigid plate similar to plate 2 of FIGS. 5 to 12.

On either side of bending lines 20" and 21" the rear walls 39 and 36 of the box are bent inwardly at 41 and 42 to enclose the portion of the box between the hinge 40 and the end walls of the box when the cover is in closed position. In this application of the invention, edges of the base and cover of the box provide stops for-the hinge in the closed position. As shown, the total angular movement of the base and cover is slightly over It is desirable that there be only sufficient pressure applied to the cover by spring arm 16" to hold it closed when the cover is closed as shown in FIGS. 14 and 15.

If spring arm 16 is deflected from its non-deflected position shown in FIG. 13 for long periods of time, it may lose some of its memory, i.e., its tendency to return to its original position. Therefore, the relative position of bending lines 17 and 20", 21" is adjusted so that in the closed position of the box, spring arm 16" has returned from its transitional position of maximum deflection rela- 7 tive to rear wall 39 to the position of comparatively slight deflection shown in FIG. 14. In FIGS. 13 and 14 the offset of spring arm 16 relative to the rear wall of the cover is indicated by b. In FIG. 14, this offset is slightly less than in FIG. 13, showing slight deflection from normal sufficient to keep the cover in closed position but insufficient to cause any appreciable permanent deflection of spring arm 16".

In the open position of the box shown in FIG. 13, the plane of the rear walls 36 and 39 is angled slightly outwardly at a large obtuse angle from bending lines 20", 21".

The interior of the box is shown as being provided with two clamping parts 43 having serrated inner surfaces to hold a ring 44 therebetween.

The inner surfaces may be coated with flocking and the outside may be provided during manufacture with a suitable embossed design. The injection moulding tool used in the manufacture of the illustrated ring box requires no complex sliding parts in order to permit the ring box to be removed therefrom, since the ring box has no undercuts.

A one-piece box of the foregoing type has the great advantages of simplicity and corrosion resistance, and it is relatively inexpensive to manufacture.

It will be understood that various other articles, such as lids, caps, covers, doors and almost anything using a spring hinge may be moulded in one piece in accordance with this invention. It also will be observed that by suitable modifications, the angle at which the hinge applies its hold-closed effect and amount of clamping hold-closed force may be varied, and that the invention is applicable to hinges which constantly return to open position as well as to hinges that will stay in both closed and open positions.

What I claim is my invention is:

1. A unitary hinge of a thermoplastic material comprising; two plate members; a first flexible portion formed integral with said plate members and joining said plate members together for pivoting movement with respect to each other; a resilient member formed integral with one of said plate members and resiliently movable with respect thereto; and a connecting arm formed integral with the other of said plate members and with a part of said resilient member remote from said one plate mem- 'ber and extending between said part of said resilient member and said other plate member, said connecting arm being provided with second and third spaced apart flexible portions disposed to enable said connecting arm to pivot about said second flexible portion relative to said other plate member and about said third flexible portion relative to said resilient member, said first, second and third flexible portions constituting first, second and third flexible bending lines respectively with said second flexible bending line being positioned closer to said other plate member than to said resilient member and said third flexible bending line being positioned closer to said resilient member than to said other plate member,

, said first and third flexible bending lines being offset with respect to each other in such a manner that movement in one direction of one of said plate members relative to the other of said plate members from at least one position to another position thereof causes pivoting of said connecting arm about said second and third flexible bending lines and a deflection of said resilient member suflicient to create a restoring force tending to return said plate members to said one position.

2. A unitary hinge of a thermoplastic material comprising; two plate members; a first flexible portion formed integral with said plate members and joining said plate members together for pivoting movement with respect to each other; a resilient member formed integral with one of said plate members and resiliently movable with respect thereto; and a connecting arm formed integral with the other of said plate members and with a part of said resilient member remote from said one plate member and extending between said part of said resilient member and said other plate member, said connecting arm being provided with second and third spaced apart flexible portions disposed to enable said connecting arm to pivot about said second flexible portion relative to said other plate member and about said third flexible portion relative to said resilient member, said first, second and third flexible portions constituting first, second .and third flexible bending lines respectively with said second flexible bending line being positioned closer to said other plate member than to said resilient member and said third flexible bending line being positioned closer to said resilient member than to said other plate member, said first and third flexible bending lines being laterally offset with respect to each other and also being offset with respect to each other in a direction substantially perpendicular to the lateral offset between said first and third flexible bending lines.

3. A unitary hinge as set forth in claim 2 in which the hinge is moulded.

4. 'A unitary hinge as set forth in claim 2 in which said thermoplastic material is polypropylene.

5. A unitary hinge as claimed in claim 2 in which said connecting arm is bent inwardly intermediate said second and third flexible bending lines.

6. A unitary hinge as set forth in claim 2 in which said resilient member is disposed in angular relation to the plane of said one plate member.

7. A unitary hinge as set forth in claim 1 in which the major portion of the outer surface of said resilient member is disposed substantially in the plane of the outer surface of said one plate member.

8. A unitary hinge as claimed in claim 7 in which said part of said resilient member extends outwardly at an angular relation to said major portion of said outer surface of said resilient member.

9. A unitary hinge as claimed in claim 8 in which said part of said resilient member is tapered or gradually reduced in thickness.

10. A unitary hinge as claimed in claim 3 in which the hinge is moulded with the major surfaces of said plate members in the angular relationship in which they will normally tlie, whereby they will tend to return to such original relationship.

11. A unitary hinge as set forth in claim 2 in which said first and third flexible bending lines are offset such that when said plate members are pivoted relative to one another beyond a transitional position, said resilient member will tend to bias said plate members to a position at a predetermined angle to their original positions.

12. A unitary hinge as set forth in claim 11 in which said predetermined angle is substantially 13. A unitary hinge as set forth in claim 2 in which said first and third flexible bending lines are offset such that when said plate members are pivoted relative to one another, said resilient member will tend at all angles to bias them to their original positions.

14. A unitary hinge of a thermoplastic material comprising; two plate members; a first flexible portion formed integral with said plate members and joining said plate members together for pivoting movement with respect to each other; a resilient member formed integral with one of said plate members and resiliently movable with respect thereto; and a connecting arm formed integral with the other of said plate members and with a part of said resilient member remote from said one plate member and extending between said part of said resilient member and said other plate member, said connecting arm being provided with second and third spaced apart flexible portions disposed to enable said connecting arm to pivot about said second flexible portion relative to said other plate member and about said third flexible portion relative to said resilient member, said first, second and third flexible portions constituting first, second and third flexible bending lines respectively with said second flexible bending line being positioned immediately adjacent said other plate member and said third flexible bending line being positioned immediately adjacent said resilient member, said first and third flexible bending lines being laterally offset with respect to each other and also being offset with respect to each other in a direction substantially perpendicular to the lateral offset between said first and third flexible bending lines in such a manner that movement in one direction of one of said plate members relative to the other of said plate members from at least one position to another position thereof causes pivoting of said connecting arm about said second and third flexible bending lines and a deflection of said resilient member suflicient to create a restoring force tending to return said plate members so said one position.

15. A unitary hinge as set forth in claim 14 iniwhich said first and third flexible bending lines are offset such that when said plate members are pivoted relative to one another beyond a transitional position, said resilient member will tend to bias said plate members to a position at a predetermined angle to their original positions.

16. A unitary hinge as set forth in claim 14 in which said first and third flexible bending lines are offset such that when said plate members are pivoted relative to one another, said resilient member will tend at all angles to bias them to their original positions.

17. A unitary hinge as set forth in claim 14 in which there are two of said first flexible portions, said resilient member and said connecting arm being disposed therebetween.

18. A hinged article having moulded integrally therewith a hinge constructed as set forth in claim 14.

19. A box made of thermoplastic material and having a cover and a base, said cover and base each having a rear wall and side walls; a first flexible portion formed integral with said rear walls and joining said rear walls together for pivoting movement of said cover and base relative to each other; a resilient member formed integral with one of said rear walls and resiliently movable with respect thereto; and a connecting arm formed integral with the other of said rear walls and with a part of said resilient member remote from said one rear wall and extending between said part of said resilient member and said other rear wall, said connecting arm being provided with second and third spaced apart flexible portions disposed to enable said connecting arm to pivot about said second flexible portion relative to said other rear wall and about said third flexible portion relative to said resilient member, said first, second and third flexible portions constituting first, second and third flexible bending lines respectively with said second flexible bending line being positioned adjacent said other rear wall and said third flexible bending line being positioned adjacent said resilient member, said first and third flexible bending lines being laterally offset with respect to each other and also being offset with rsspect to each other in a direction substantially perpendicular to the lateral offset between said first and third flexible bending lines in such a manner that movement in one direction of one of said rear walls relative to the other of said rear walls from at least one position to another position thereof causes pivoting of said connecting arm about said second and third flexible bending lines and a deflection of said resilient member sufficient to create a restoring force tending to return said rear walls to said one position.

20. A box as set forth in claim 19 in which said first and third flexible bending lines are offset such that when said rear walls are pivoted relative to one another beyond a transitional position, said resilient member will tend to bias said rear walls to a position at a predetermined angle to their original positions.

21. A box made of thermoplastic material as set forth in claim 20 in which edges of said cover and base engage when said cover is closed and act as stops to limit the closing movement of the box to less than 22. A box made of thermoplastic material as set forth in claim 21 in which the parts of said rear walls between said first flexible bending line and said side walls are directed inwardly to enclose the rear of said box in closed position.

References Cited by the Examiner UNITED STATES PATENTS 3,009,169 11/1961 Bodner 16--l50 3,043,354 7/1962 Fitzgerald 16150 3,186,574 6/1965 Davidson 16-150 3,205,530 9/1965 Van Buren 16150 BOBBY R. GAY, Primary Examiner.

D. L. TROUTMAN, Assistant Examiner. 

1. A UNITARY HINGE OF A THERMOPLASTIC MATERIAL COMPRISING; TWO PLATE MEMBERS; A FIRST FLEXIBLE PORTION FORMED INTEGRAL WITH SAID PLATE MEMBERS AND JOINING SAID PLATE MEMBERS TOGETHER FOR PIVOTING MOVEMENT WITH RESPECT TO EACH OTHER; A RESILIENT MEMBER FORMED INTEGRAL WITH ONE OF SAID PLATE MEMBERS AND RESILIENTLY MOVABLE WITH RESPECT THERETO; AND A CONNECTING ARM FORMED INTEGRAL WITH THE OTHER OF SAID PLATE MEMBERS AND WITH A PART OF SAID RESILIENT MEMBER REMOTE FROM SAID ONE PLATE MEMBER AND EXTENDING BETWEEN SAID PART OF SAID RESILIENT MEMBER AND SAID OTHER PLATE MEMBER, SAID CONNECTING ARM BEING PROVIDED WITH SECOND AND THIRD SPACED APART FLEXIBLE PORTIONS DISPOSED TO ENABLE SAID CONNECTING ARM TO PIVOT ABOUT SAID SECOND FLEXIBLE PORTION RELATIVE TO SAID OTHER PLATE MEMBER AND ABOUT SAID THIRD FLEXIBLE PORTION RELATIVE TO SAID RESILIENT MEMBER, SAID FIRST, SECOND AND THIRD FLEXIBLE PORTIONS CONSTITUTING FIRST, SECOND AND THIRD FLEXIBLE BEDING LINES RESPECTIVELY WITH SAID SECOND FLEXIBLE BEINGING LINE BEING POSITIONED CLOSER TO SAID OTHER PLATE MEMBER THAN TO SAID RESILIENT MEMBER AND SAID THIRD FLEXIBLE BENDING LINE BEING POSITIONED CLOSER TO SAID RESILIENT MEMBER THAN TO SAID OTHER PLATE MEMBER, SAID FIRST AND THIRD FLEXIBLE BENDING LINES BEING OFFSET WITH RESPECT TO EACH OTHER IN SUCH A MANNER THAT MOVEMENT IN ONE DIRECTION OF ONE OF SAID PLATE MEMBERS RELATIVE TO THE OTHER OF SAID PLATE MEMBERS FROM AT LEAST ONE POSITION TO ANOTHER POSITION THEREOF CAUSES PIVOTING OF SAID CONNECTING ARM ABOUT SAID SECOND AND THIRD FLEXIBLE BENDING LINES AND A DEFLECTION OF SAID RESILIENT MEMBER SUFFICIENT TO CREATE A RESTORING FORCE TENDING TO RETURN SAID PLATE MEMBERS TO SAID ONE POSITION. 